How can the fact that fish and dolphin have similar organs and similar general shape be explained?

The similar organs and general shape of fish and dolphins can be explained by convergent evolution, where unrelated species evolve similar traits due to adapting to comparable environments or ecological niches. Both fish and dolphins are adapted to life in water, leading to streamlined bodies and similar physiological features for efficient swimming. Despite their differences in ancestry—fish being aquatic vertebrates and dolphins being mammals—these adaptations illustrate how similar functional demands can shape the evolution of different species.